Lubricating oil



Reece it i Shoemaker, Hammond, Ind., assignors to Stand- -t ard OilCompany, Chicago, Ill, a corporation of 1 Indiana No Drawing.

Application August 31, 1935, Serial No. 98,734

7' Claims. (01. 252-41) This invention relates to improvements inlubricating oils, and particularly, to corrosion inhibited lubricatingoils.

In order to obtain increased acceleration and ii increased speed inpresent day internal combustion engines it has become necessary toincrease both the thermal and mechanical stresses 18 metal bearings,suchas copper-lead, cadmiumnickel and cadmium silver bearings have, to alarge extent, replaced Babbitt metal bearings.

While mechanically the new type of metal bearings has provensatisfactory, there have been 20 an unusually large number of bearingfailures due to corrosion. It has also been noted that the corrosion ofhard metal alloy bearings has been more markedwith highly refinedlubricatingoils. i 26 By highly refined lubricating oils we mean oilswhich have been subjected to such a refining process, for example,solvent extraction, that the paraffinicity of the .oil is markedlyincreased.

It has been found that highly refined lubri- 30 eating oils causecorrosion of cadmium-silvervalloy bearings to the extend of 5 mgs. percm. and even greater when bearing-s'are submerged for 25 hours or lessin an airagitated oil which has been preoxidized at about 340 -F. for 25to 50 I, hours.

These highly refined lubricating oils have a minimum viscosity range ofa5. A. E. 10 oil. Our

invention contemplates the use of highly" re--' fined lubricating oilsper se or mixtures of high- 40 1y refined lubricating oils, or mixturesof-corrosi ve oils and non-corrosive oils, such as a corrosive oilandlubricating oil fractions from-.Winkler Crude or crudes of theWinkler type.

It is, therefore, an object of our invention to provide a highly refinedmotor oil which will not corrode bearings of the cadmium-silver andcopper-lead type. Another object of our invention is to provide acorrosion inhibitor, which, when added to a highly refined lubricatingoil, will prevent the corrosion.- of hard metal bearings suchas'copper-lead and/or cadmium-silver metal bearings and which will not bedetrimental to other desir-- able properties of the motor oil.

A further object of our invention is to provide dodecyl thiocyanatepredominates.

a motor oil containing a very small amount of an organic material whichwill inhibit the'cor rosion of bearings in internal combustion engines., g Wehave found that the foregoing objects may ,8 be attained byadding toa highly refined motor 011 up to 1%, but preferably 0.01% to0.75% of certain organic materials, particularly, long straight chainalkyl thiocyanates and/or long straight chain allgvl isothiocyanateshaving the 10 general formula RSCN or RNC S where R is an alkyl group.Our invention contemplates the use of alkyl thiocyanates having 8 to 14carbon atoms and preferably the alkyl thiocyanates having 12 carbonatomsin the alkyl radical, or a mixture 15 of alkyl thiocyanates such asdodecyl, octyl, decyl and tetradecyl thiocyanates, but in which the Ourinvention also contemplates the use of alkyl isothiocyanates having 8 to14 carbon atoms in the alkyl go radical and preferably'the alkylisothiocyanates having 12' carbon atoms in the alkyl radical, or amixture of alkyl isothiocyanates such as dodecyl, octyl, decyl andtetradecyl isothiocyanates, .but in which the dodecyl isothiocyanate 25predominates.

We have found that a very effective corrosion inhibitor is obtained whendodecyl thiocyanate or a mixture of allsvl thiocyanates, in which thedodecyl thiocyanate predominates besides small 30 amounts of octyl,decyl, and tetradecyl thiocyanates, is heated in a sealed tube at atempera;- ture of about 350 F. for about three days. The resultantproduct may be used as such or fractions thereof may be employed. Theproduct 35 may be vacuum distilled under about 1 pressure and the firstninety percent over used as the corrosion inhibitor or we may extractthe product with hot alcohol at about -180 F. and the alcohol insolubleportion used, although 4 the alcohol soluble portion may also be used ascorrosion inhibitor. Other-solvents, particularly very-low boilinghydrocarbons such as propane may be used. g

We believe that by heating the thiocyanates in 45 the above manner, thesame are converted to a substantial degree to the isothiocyanates.However, other products may be formed in the'heat-.

mentioned compounds as corrosion inhibitors in motor oils we have testedthe same in a highly refined motor oil under severe engine operatingagitating the same at about 341 F. The corrosion inhibitor and theweighed bearings are placed in the preoxidized oil and the oil air-agi--tated at about 341 F. The bearings are removed at periodic intervals,washed free of oil and the loss in weight determined.

Test 2.-In this test the weighed bearings are placed in a highly refinedoil containing the inhibitor and is air agitated at about 341 F. Atperiodic intervals the bearings are removed from the oil bath, washedfree of oil and the loss in weight determined. Each time before beingreplaced in the oil bath the bearings are polished bright and reweighedand again tested for predetermined periods. This test differs from testNo. 1 in that the test is started with an unoxidized highly refined oiland the test bearings are polished at predetermined intervals.

Test 3'.In this test the oil containing the corrosion inhibitor istested in a six cylinder internal combustion engine operating undersevere conditions of 2500 R. P. M. at 25 B. H. P. output with a wateroutlet temperature of about F. and

an oil sump temperature of about 320 F. The length of operation beforebearing failure is a measure of the effectiveness of the corrosioninhibitor.

In each of the above tests the oil used was a motor oil refined to suchan extent that a loss in weight of more than 5 mg. per cm. is obtainedin 25 hours or less on a cadmium-silver alloy bearing submerged in anair agitated oil at 340 R, which oil has been preoxidized for 25-50hours at about 340 F.

Table I shows the effectiveness of 0.2% of lauryl thiocyanate in ahighly refined motor oil as evaluated by Test 1 described above.

Table I Hours of test Loss in mga [cm 1 Control (preoxidized 50 hrs.) 6.0 41. Control+0.2%lauryl thiocyanate. 0. 0 0.0 0. 9 5. 7

In Table II are tabulated the results obtained with lauryl thiocyanateand lauryl isothiocyanate as evaluated by Test 1 with a 25 hourpreoxidi'zed oil.

The above results demonstrate the efiectiveness of the alkylthiocyanates and alkyl isothiocyanates of the, hereinbefore mentionedtype in preventing the corrosion of cadmium-silver bearings.

Test 1.-.In this test a highly refined 011, to which the corrosioninhibitor is tobeadded, is preoxidized for either 25 hours or 50 hoursby air In Table III we have tabulated results obtained by test methodNo- 2 described above.

In the engine tests described above as Test No. 3 the efiectiveness ofthe corrosion inhibitors in an oil has been tested in a six cylinderengine operating at 2500 R. P. M. with a 25 B. H. P. output and a wateroutlet temperature of about 180 F. The oil sump was maintained at atemperature of about 320 F. Using a highly refined S- A. E. 20 oilcontaining 0.5% of lauryl thiocyanate the bearing failed in 19 hours.With 0.5% of lauryl isothiocyanate in a sample of the same oil theengine ran for 35 hours without bearing failure. With a sample of thesame oil containing no corrosion inhibitor the bearings failed in 12hours. It should be observed that the above operating conditions aremuch more severe than those encountered under average actual drivingconditions. Under average driving conditions the bearings would lastmuch longer.

While we have illustrated our invention in connection with the foregoingexamples, we do not wish to limit our invention to the same. Theseexamples are merely illustrative and not a limitation upon the scope ofour invention.

Where used hereinbefore and in the appended claims, the term laurylthiocyanate is used to define an alkyl thiocyanate having 8 to 14 carbonatoms in the alkyl chain but predominantly a dodecyl thiocyanate withsmall amounts of octyl, decyl, and tetra decyl thiocyanate. The termlauryl isothiocyanate as used hereinbefore and in the appended claims isused to define the isothiocyanate of the above compounds.

We claim:

1. The method of preventing the corrosion of bearing metal alloysselected from the group consisting of cadmium-silver, cadmium-nickel andcopper-lead alloys in the presence of a highly refined lubricating oilnormally corrosive to said metal alloys in internal combustion engineswhich comprises adding to said lubricating oil a substantial amount butnot more than 1% of an alkyl thiocyanate' having 8 to 14 carbon atoms inthe alkyl radical.

2. The method of preventing the corrosion of bearing metal alloys havingthe corrosive susceptibility of alloys of the class consisting ofcadmium-silver, cadmium-nickel and copper-lead alloys in the presence ofa highly refined l'ubrlcating oil normally corrosive to said bearingmetal alloys in internal combustion engines which comprises adding tosaid lubricating oil from about 0.01% to about 1% of an alkylisothiocyanate having 8 to 14 carbon atoms in the alkyl radical, wherebysaid highly refined lubricating oil is rendered non-corrosive to saidbearing metal alloys. 1

3. The. method of preventing the corrosion of bearing metal alloyshaving the corrosive susceptibility of alloys of the class consistingofcadmium-silver, cadmium-nickel and copperlead alloys in the presenceof a. highly refined tibility of alloys of the classconsisting orcadmium-silver, cadmium-nickel and copper-lead alloys in' the presence01' a highly refined lubricating oil normally corrosive to said bearingmetal alloys in internal combustion engines which comprises adding tosaidlubricating oil from about 0.01% to 1%of a mixture of alkylisothiocyanates having more than seven carbonatoms in each alkylradical, said mixture of alkyl isothiocyanates comprising predominantlydodecyl isothiocyanates and small amounts of octyl, decyl, andtetradecyl isothiocyanates, whereby said highly refined lubricating oilis made non-- corrosive to said bearing metal alloys.

5. The method of preventing the corrosion ofbearing metal alloys havingthe corrosive susceptibility of alloys of the class consisting ofcadmium-silver, cadmium-nickel and copperlead alloys in the presence ofa highly refined o isothiocyanate having 8 to 14 carbon atomsinlubricating oil normally corrosive to said bearing= metal alloys ininternal combustion engines which comprises adding to said lubricatingoil a sub-. stantial amount but not more than about 1% of an organiccompound selected from the group consisting of an alkyl 'thiocyanatehaving 8 to 14 carbon atoms in the alkyl radical and an alkyl the alkylradical'whereby corrosion of said bearinhibited.

7; A method of lubricating bearing surfaces" ing metal alloys by saidhighly refined lubricating oil is inhibited.

6. The method of preventing the corrosion of bearing metal alloys havingthe corrosive sus; ceptibility of alloys of the class consisting ofcadmium-silver, cadmium-nickel and copper-lead alloys in the presence ofa highly refined lubricating oil normally corrosive to said bearingmetal alloys in internal combustion engines which comprises adding tosaid lubricating oil from about 0.01% to 1% of an organic compoundselected from the group consisting of a mixture of alkyl thiocyanateshaving more than seven carbon atoms in each alkyl radical, said mixtureof alkyl thiocyanates comprising predominately dodecyl thiocyanates andsmall amounts of octyl, decyl and tetradecyl thiocyanates, and a mixtureof alkyl isothiocyanates having more than seven carbon atoms in eachalkyl' radical, said mixture of alkyl isothiocyanates comprisingpredominately dodecyl isothiocyanates and small amounts of octyl, decyland tetradecyl isothioalloys by said highly refined lubricating'oil iswhich comprises maintaining between metallic bearing surfaces, one ofwhich is an'all'oy containing a characterizing proportion of a,metalselected from cadmium-silver, copper,-lead and nickel, a film oflubricating oil normally eifectiive to provide lubrication of thebearing surfaces but whichswould normally tend to corrode the surface ofthe aforesaid alloy, said lubricating oil having incorporated thereindodecyl isothiocyanate, in small amount suflicient substantially toretard corrosion of the surfaces of said alloys by said oils.

CLARENCE M. LOANE.

BERNARD H. SHOEMAKER.

' cyanates whereby corrosion to said bearing metal

